Amid mixed signals, Japan rates nuclear crisis at highest severity level

TOKYO — Japanese authorities issued contradictory assessments Tuesday about the severity of the crisis at the Fukushima Daiichi nuclear plant, with Prime Minister Naoto Kan saying that the situation is improving “step by step” and a senior official from the operating power company warning of further mass radiation releases.

The mixed signals provided a backdrop to a decision earlier in the day by Japan’s nuclear agency to raise the severity rating of the nuclear crisis at Daiichi from Level 5 on the International Nuclear and Radiological Event Scale (INES), indicating an “accident with off-site risk,” to Level 7, a “major accident” on a par with the 1986 Chernobyl disaster.

Loading...

Comments

• Weigh In
• Corrections?

Personal Post

Video

Japan raised the crisis level at its stricken nuclear power plant to 7, the highest on an international scale and on a par with the 1986 accident at Chernobyl. (April 12)

Gallery

 After the earthquake and tsunami, entire towns in Japan have been destroyed. But search-and-rescue teams are fanning out in what will be a lengthy, complex endeavor.

The reassessment came amid reports from the International Atomic Energy Agency that the plant is showing “early signs of recovery” but remains in critical condition. The upgraded severity reading does not reflect a recent deterioration at the plant. Rather, it suggests Japan’s evolving understanding of the damage that occurred there one month ago and the contamination that has been leaking since.

The most severe radiation leak occurred in the 48 hours after a March 15 hydrogen explosion at the unit 2 reactor, Japan’s Nuclear and Industrial Safety Agency said. Nuclear experts said Tuesday that the government waited too long to upgrade the INES rating, given the vast amounts of radiation being released.

“Monitoring data available shows that, in my view, the government probably knew around March 16, 17 or 18 that it would reach Level 7,” said Hironobu Unesaki, a professor at the Kyoto University Research Reactor Institute. “Their response has been extremely regrettable. The government is being very careful not to cause unnecessary panic, but they are being too cautious.”

At a news conference in Tokyo to announce the new INES rating, Hidehiko Nishiyama, deputy chief of the Nuclear and Industrial Safety Agency, emphasized that radiation released from Fukushima Daiichi amounted to less than one-tenth the total released from Chernobyl. Later in the day, Kan said radiation levels around the plant were steadily dropping.

Those calming messages, though, were undercut at another separate news conference, during which an official from Tokyo Electric Power Co., the plant’s operator, said the company’s concern was “that the amount of leakage could eventually reach that of Chernobyl or exceed it.”

That stark assessment reinforced apprehension that this nuclear emergency will cause greater problems than those first predicted by the government, which has played down long-term safety concerns and only Monday expanded its mandated 12-mile-radius evacuation zone.

On Tuesday, Kan defended the government’s response, saying that its decision to recategorize Fukushima as a Level 7 event “does not show that we delayed or underestimated the nuclear situation.”

A Level 7 accident, according to the INES scale, is typified by a “major release of radioactive material with widespread health and environmental effects.” The scale was established by the IAEA about 20 years ago, but its guidelines leave much room for interpretation, nuclear experts say.